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Search: id:A101416
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| A101416 |
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Nearest k to j such that k*(2^j-1)-1 is prime where j=A000043(n) and 2^j-1 = Mersenne-prime(n) = A000668(n). If there are two k values equidistant from j, each of which produces a prime, the larger of the two gets added to the sequence. |
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2
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| 2, 2, 2, 6, 20, 14, 32, 90, 72, 80, 230, 80, 560, 740, 1542, 1782, 450, 828, 2562, 3936, 12474, 9288, 10224, 16022, 11088, 31034, 53972, 92372
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OFFSET
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1,1
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EXAMPLE
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n=7, j=A000043(7)=19, A000668(7)=524287, then k=6 or k=32 are the nearest values to j which produce primes so we take the larger of the two k values for a(7)=32.
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CROSSREFS
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Cf. A000043, A000668, A098555, A159585.
Sequence in context: A058756 A007039 A025248 this_sequence A098920 A129365 A021453
Adjacent sequences: A101413 A101414 A101415 this_sequence A101417 A101418 A101419
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KEYWORD
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hard,nonn
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AUTHOR
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Pierre CAMI (pierrecami(AT)tele2.fr), Jan 16 2005
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EXTENSIONS
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a(5)=20, a(20)=3936 corrected, other terms verified, a(27)-a(28) extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Apr 16 2009
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